The nuclear reaction .sup.10 B(n,.alpha.).sup.7 Li has been used in boron neutron capture therapy to cure malignant gliosarcomas implanted in the hind legs of mice [Farr et al., Int. J. Appl. Radiot. Isotopes, 19, 459 (1968)]. More recently, this reaction has been used in boron neutron capture therapy to cure spontaneous malignant melanomas in pigs [Mishima et al., Proc. First Int. Symp. Neutron Capture Therapy, Eds. R. G. Fairchild and G. L. Brownell, Brookhaven National Laboratory, Report BNL 51730, p. 355, 1983]. The sulfhydryl borane monomer [B.sub.12 H.sub.11 SH].sup.2- as the sodium salt is used as a .sup.10 B carrier for boron neutron capture therapy of malignant human brain tumors [Hatanaka et al., Modern Neurosurgery, Ed. M. Brock, Springer, Berlin, p. 122, 1982].
The general principle of boron neutron capture therapy, enunciated in the radiological literature decades ago, is based on the physical property of the boron-10 nucleus to strongly interact with thermal neutrons. This approach to cancer therapy is based on the liberation of high energy ionizing radiation in boron-10 enriched tumor tissue during neutron irradiation. The incident thermal neutrons have a relatively low energy (0.025 eV) which gives rise to a very high energy alpha particle (2.4 MeV) from the .sup.10 B(n,.alpha.).sup.7 Li reaction following neutron capture by boron-10.
The major requirements for successful application of boron neutron capture therapy are: First, there must be a large concentration of .sup.10 B in all microscopically viable areas of the neoplasm (&gt;15 .mu.g of .sup.10 B per gm of tumor). This requires that the boron compound be injected through blood vessels rather than directly into the suspected tumor area since the precise dimensions and configuration of the invasive neoplastic process are not clearly delineated from the surrounding normal tissue. Second, a source of neutrons must be available to irradiate the neoplastic area with sufficient numbers of thermal neutrons to cause destruction of cells containing boron-10.